In my case the taskbar comes up after 1 - 4 (maximum counted) attemptings with a site reload.
It doesn't matter if i clean up the cache with Crtl+F5 or just reload with F5.

As written both in IE and FF.

Although the behaviour isn't the same i would suggest that the problem will be found at the same place, what will be strange cause of same browsers and ext version. I think the difference rub's on variating browser and system settings.